Browsing by Author "Şenol, H."
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Conference paperPublication Metadata only Channel estimation in underwater cooperative OFDM system with amplify-and-forward relaying(IEEE, 2012) Şenol, H.; Panayırcı, E.; Erdoğan, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, MuratThis paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the resence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm, due to the reduced number of taps to be estimated. The resulting novel algorithm initially estimates the overall sparse channel taps from the source to the destination as well as their locations using the matching pursuit (MP) approach. The correlated non-Gaussian effective noise is modeled as a Gaussian mixture. Based on the aussian mixture model, an efficient and low complexity algorithm is developed based on the combinations of the MP and the space-alternating generalized improve the estimates of the channel taps and their location as well as the noise distribution parameters in an iterative way. The proposed SAGE algorithm is designed in such a way that, by choosing the admissible hidden data properly on which the SAGE algorithm relies, a subset of parameters is updated for analytical tractability and the remaining parameters for faster convergence Computer simulations show that underwater acoustic (UWA) channel is estimated very effectively and the proposed algorithm has excellent symbol error rate and channel estimation performance.Conference paperPublication Metadata only Görünür ışık kanalların modellenmesi ve ACO-OFDM için başarım analizi(IEEE, 2015) Yeşilkaya, A.; Alsan, H. F.; Miramirkhani, Farshad; Panayırcı, E.; Şenol, H.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, FarshadSpectrum scarcity of traditional radio communication has led communication engineers to find new alternatives. Indoor visible light communication is one alternative to solve this problem since its spectrum is not regulated and it has much wider bandwidth then traditional communication systems. This increased the research done in the field of visible light communications. However a proper indoor channel model is lacking and all previous studies assumes that only additive white Gaussian noise (AWGN) is present. Lack of proper channel model has motivated us to model a realistic indoor visible light channel. After modeling the indoor visible light channel, the performance of an asymmetrically clipped optical OFDM (ACOOFDM) system which is suitable for optical communications is investigated and compared to that of the AWGN optical channels.Conference paperPublication Metadata only Renkli̇ Gauss gürültülü seyrek sualtı akusti̇k kanalların kesti̇ri̇mi̇(IEEE, 2012) Erdogan, M.; Şenol, H.; Panayırcı, E.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Muratİşbirlikli sualtı kablosuz iletişim sistemleri konusu son yıllarda büyük önem kazanmıştır. Özellikle sualtı akustik kanalların seyrek (sparse) olma özelliği taşıması ve sisteme giren toplamsal gürültünün renkli Gauss gürültüsü olması sualtı kanallarının kestirimini çok zorlaştırmaktadır ve kuramsal açıdan ilginç kılmaktadır. Bu çalışmada kaynaktan hedef alıcıya iletimin role aracılığıyla ˘yapıldığı bir dik frekans bölmeli çoğullama (orthogonal frequency division multiplexing (OFDM))-tabanlı sisteme uyumlu eşleme (matching pursuit (MP)) algoritması kullanılarak kanal kestirim problemi çözülmüş¸ ve elde edilen sonuçlarda yüksek hata başarım elde edilmiştir.ArticlePublication Metadata only Sparse channel estimation and equalization for OFDM-based underwater cooperative systems with amplify-and-forward relaying(IEEE, 2016-01-01) Panayırcı, E.; Şenol, H.; Uysal, Murat; Poor, H. V.; Electrical & Electronics Engineering; UYSAL, MuratThis paper is concerned with a challenging problem of channel estimation and equalization for amplifyand- forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in sparse underwater acoustic (UWA) channels. The sparseness of the channel impulse response and prior information for the non-Gaussian channel gains, modeled by an exact continuous Gaussian mixture (CGM), are exploited to improve the performance of the channel estimation algorithm. The resulting novel algorithm initially estimates the overall sparse complex-valued channel taps from the source to the destination as well as their locations using the matching pursuit (MP) approach. The effective time-domain non- Gaussian noise is approximated well as a Gaussian noise in the frequency-domain, where the estimation takes place. An efficient and low complexity algorithm is developed based on the combinations of the MP and the maximum a posteriori probability (MAP) based space-alternating generalized expectationmaximization technique, to improve the estimates of the channel taps and their locations in an iterative way. Computer simulations show that the UWA channel is estimated very effectively and the proposed algorithm exhibits excellent symbol error rate and channel estimation performance.Conference paperPublication Metadata only Sparse channel estimation for OFDM-based underwater cooperative systems with amplify-and-forward relaying(IEEE, 2014) Şenol, H.; Panayırcı, E.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, MuratThis paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm, due to the reduced number of taps to be estimated. The resulting novel algorithm initially estimates the overall sparse channel taps from the source to the destination as well as their locations using the matching pursuit (MP) approach. The correlated non-Gaussian effective noise is modeled as a Gaussian mixture. Based on the Gaussian mixture model, an efficient and low complexity algorithm is developed based on the combinations of the MP and the space-alternating generalized expectation-maximization (SAGE) technique, to improve the estimates of the channel taps and their location as well as the noise distribution parameters in an iterative way. The proposed SAGE algorithm is designed in such a way that, by choosing the admissible hidden data properly on which the SAGE algorithm relies, a subset of parameters is updated for analytical tractability and the remaining parameters for faster convergence Computer simulations show that underwater acoustic (UWA) channel is estimated very effectively and the proposed algorithm has excellent symbol error rate and channel estimation performance.Conference paperPublication Metadata only Sualtı işbirlikli OFDM sistemleri için MP-SAGE kanal kestirimi(2013) Erdogan, M.; Şenol, H.; Panayırcı, E.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, MuratIn this paper, an efficient channel estimation algorithm is proposed for amplify-and-forward (AF) cooperative relay based orthogonal frequency division multiplexing (OFDM) system in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. The algorithm is based on the combinations of the matching pursuit (MP) and the space-alternating generalized expectation-maximization (SAGE) technique, to improve the estimates of the channel taps and their location as well as the Gaussian mixture noise distribution parameters in an iterative way. Computer simulations show that underwater acoustic channel is estimated very effectively and the proposed algorithm has excellent symbol error rate (SER) and channel estimation performance, as compared to the existing ones.